Pilot instructing device



Nov. 20, 1945. I H. B. GROW 2,389,359

PILOT INSTRUCTING DEVICE Filed June 24, 1941 2 Sheets-Sheet 1 iNV ENl OR #ARLOW E. 650W hi ATTQRNEY Nuv. 20, 1945. H. B. GROW ,3

' PILOT INSTRUCTING DEVICE I .Filed June 24, 1941 2 Sheets-Sheet 2 I 45' IIIIIHI'" INVENTOR Hfi/MQW a. 620W atente or. 29,

This invention relates to instructional or teaching devices in general, and especiallyto a device for training ,and instructing airplane pilot students to familiarize them with. the control of air craft by radio signals emanating from radio range signal stations, to the end of learning the us of such signals in aerial navigation. 7 I

While pilot training devices of more or less complicated and usually very costly constructions are known, they are mostly intended for teaching would-be pilots in the art of blind or instrument flying, while the present invention is primarily designed for the purpose of familiarizing pupil pilots with the technique of guiding a ship to a station or to a given point by radio range signals or directional radio beam signals, usually broadcast from stations located at or near airports. The signals intermittently propagated from such broadcasting stations are in the form of two basic signals, emitted from two cross secting directional antennas. One antenna emits the signal dash-dot or "N," while the other emits signal dot-dash or A."- These signal divide the area surrounding the broadcast stations into four zones, sectors or fields. In these fields there is a narrow coneshaped strip where the. signals N and Aoverlap and create a steady monotone in the form of a long dash or T signal. This is the beam or on course signal at which both signals N and A are of equal signal strength. This beam or on course or T signal, being sometimes called the leg, forms the guiding line for a plane to ride home onto the airfield. In the areas between the four beams the signals "N and A are variously distinguishable. In zones immediately adjacent to the beams there will be a narrow-area in which only a very slight variation between the strength of either signals N or A may be distinguished. This area is called the twilight band bordering beam. In zones further remote from the beam, the signals A and N will vary in their respective strength, depending at which side of the beam the signals are received. These zone are called the bi-signal zones. There is an A bi-signal zone and an N bi-signalzone, wherein the A and N signals, respectively, predominate. The further away the place of reception, the less of one signal will be heard and the more of the other signal, until only one of the signals will be heard. In such zone where only one signal is heard an airplane would be oft-course.

At the center of each of the four areas, or just above the broadcasting station, neither of the N" or A signals can be heard. This area just above the station is called the cone of silence," at which the signals go dead." Evidently the area oi this cone of silence grows larger with the distance directly above the broadcasting station. The broadcast stations transmitting the guide signals are preferably so arranged that each pair of beams are at right angles to the other pair.

The foregoing explanation of ,the arrangement of a complete radio range signal field is essential for the purpose of explaining my device, which latter i intended to simulate a complete radio range signal field, as well as a ship or airplane. intended to be guided by the pupil pilot in accordance with the emissions of signals from such' signal field.

It is the object of this invention to produce an inexpensive, simple and eiilcient pilot training device, which will simulate an existin radio range station and an airplane in flight in respect to such station, and wherein means are provided for controlling the flight of a simulated airplane by the pupil pilot in accordance with the signals received automatically from the simulated station. The foregoing and still further objects 01' this invention will become more fully apparent from the ensuing description, in connection with the Fig. 4 is an enlarged detail view of a drive mechanism, indicated at the left of Fig. 3;

Fig. 5 is a detail view of the flight or plane indicator or rider;

Fig. 6 is a cross section therethrough in one'oi.

its preferred forms;

Figs. 7 and 8 illustrate portions of quadrant bars connected by resistances 01 various forms;

Fig. 9 is a detail view showing a portion of a quadrant bar, with its resistance and a contact arm with glide contact;

Fig. 10 is a dlagrammatical modification of a signal volume control device; and

Fig. 11 is a modification of a ship or alrcrai't simulating rider in the form ofa scriber.

Referring now more specifically to Figures 1 and 2, numeral lo denotes a substantially closed casing, preferably provided with a translucent removable cover I l, which latter may be in the form of a ground glass or may take the shapeoi a record sheet backing or support, as will be presently explained. Into casing l leads a conduit 12 from a power source, indicated at H in Fig. 2. From casing l0 extends a cable l4, which leads to the pupil-manipulated control instrument l5, shown diagrammatically in Fig. 2, and which instrument comprises a hand wheel IS, a compass rose ll, two resistances l8 and I9, and an earphone volume control 20, which latter may be set for accommodating the hearing of the individual students. Another cable 2| extends from casing I0 and connects with a signal receiver, shown at 22 in Fig. 2 in the form of earphones, adjustable by variable volume control 20, seen diagrammatically in that figure.

Within casing ID are located all instrumentalities for simulating a complete radio range signal station and an airplane in flight, as well as means for operating them. There are provided four arcuated and overlapping quadrant bars I, II, III and IV, arranged in a circle and adjustable relative to one another, representing the four legs and fields of a broadcast station. Each of the quadrant bars consists of two electrically and bodily separated segments or sections, such as sections 23 and 24 of bar I, sections 25 and 26 of bar 11, sections 21 and 28 of bar III, and sections 29 and 30 of bar IV. The bottom ends of each two adjacent sections of each quadrant bar are preferably connected by an insulating member 3 I,

shown clearly in Fig. 3, while the upper ends are bridged by insulated electrical resistances indicated at 32 in Figs. 2, '7 and 8. These resistances may be arranged in several ways, two forms of which are shown in Figs. 7 and 8. In Fig. 7 a single resistance 32' is indicated, which is insulated at 33 from the body of sections 23 and 24, to which latter the ends of the resistances are secured at 34 and 35. Another form of bridging resistances is shown in Fig. 8 where two resistances 36 and 31 are employed, which are also insulated at 38 from bar sections 23 and 24. Resistance 36 is electrically connected at 39 to bar section 23, whereas resistance 31 is electrically secured at 40 to bar section 24.

All quadrant bars or units are adjustable in units at 42, is a contact bar 43 shown in one of its forms in Figures 2 and 3. This bar consists of two conductive legs 44. and 45, which are connected together by an insulating centerpiece 46. Depending from the lower surface of legs 44 and 45 of bar 43 are glide or brush contacts 44 and 45', seen clearly in Figs. 3 and 9. These contacts engage the upper surfaces of the quadrant units and establish positive electric connections between the legs of bar 43 and the quadrants. The ,bar is grooved for the reception of pin 41 (see Figs. and 6), which extends downwardly from a mounting 48 of an aircraft simulating indicator or rider 49. The latter may be in the form of an electric bulb, supplied by an independent source of ener y, not shown. The light of the bulb is intended to indicate the course imparted to the Mounting 48 of the ship or flight indicator is held in the slots of non-conductive or insulated control bars 50 and Bi, the movement of which bars is intended to change the postion of indicator 49 relative to the quadrant bars, represented by the four sectors of the device. At one end of each of these bars there is arranged a gear casing 52, shown in detail in Fig. 4, within which casings are journalled threaded shafts 53 and 53 (see Fig. 2), and grooved shafts 54 and 54'. Between the two flanges or walls of each casing 52 are held two meshing gears in engagement with the shafts. Gears 55 are provided with an internal thread. engaging the thread of shafts 53 and 53', while gears 56 are each equipped with a key 51 which is designed to glide in the groove or slot of shaft 54 or 54. The threaded shafts 53 and 53 are driven, through worm gear units 58 and 58', by constant speed motors 59 and 59', whereas slotted shafts 54 and 54' are operated, through worm gear units 60 and 60', by variable speed motors SI and GI. Motors 59 and 59' may also be of the variable speed type, if desired, but for the sake of simplicity only one set of motors is shown to be of variable speed.

The ratio of gears 55 and 56 is shown to be one to one, although such ratio may be varied if found more advantageous. Beneath slotted bars 50 and 5!, near the gear casings, are mounted brush or glide contacts 32 and 53, which are adapted to ride over electrical resistances 64 and 65, the latter being tapped at their centers as indicated at 54' and 65'. Arranged also in the casing I0 is a signaling device, consisting of a motor 66, upon the shaft of which are mounted interrupter wheels Bland 63, against which bear glide contacts 69 and Ill. Interrupter wheels 61 and 88 are designed to produce, respectively, the signals N" and A, which are passed from an oscillator H to a signal receiving instrumentality, such as a loudspeaker or earphones 22.

Electric connections In observing Fig. 2 it will be noted that all instrumentalities within. casing l0 and without are supplied by a single source of energy l3. From one of the conductors l2, supplied by that source; branches ofi conductor 13, which leads to motor 59. The latter is connected along with variable speed motor 6| to the ground. From motor St a conductor 14 connects at 15 with the resistance l9, located in the pupil-manipulated control instrument I5 (see Figs. 1 and 2). Control post 16 of the instrument is connected through leads l1, l8 and I9 to conductor 12. To posts 16 are secured glider contacts 30 and 8! (see Fig. 1), which are mounted in line with one another, as diagrammatically indicated in the lower left-hand corner of Fig. 2. These glider contacts ride over resistances l9 and I3, respectively. Resistance 19 controls the speed of motor 6|, while resistance l8 controls and varies the speed of motor 61'.

The wiring of the control for variable speed motor 6| is similar to that explained in connec: tion with motor 6|. From conductor 12, continuing through lead 19 and 18, there extends a wire 32 to motor 59'. From this motor current passes to the ground along with current from the grounded side of variable speed motor S'l', while from the other terminal of motor 6| a wire 93 connects witlrtap' 94 of resistance l8. It will be noted that both resistances l8 and I9 are circular in shape and are endless, and that their taps 84 and 15 are offset at 99 degrees to one another. Thus when glide contacts 89 and 9|, riding simultaneously over resistances |9 and I8, respectively, assume a position in line with connecting tap 15, there will be no resistance in the circuit controlling motor 6|, in consequence whereof the motor will operate at its maximum speed. At the same time in the circuit controlling motor 6| the cur rent is forced to pass primarily through one quarter of resistance I 9, thereby causing motor 9| to operate at medium speed. When the contacts assume a position over tap 84, full current will flow in the circuit controlling motor 6|, thus causing the latter to operate at. its maximum speed, while in the circuit controlling motor 6| the current now mustpass primarily through one quarter of resistance l9, whereby motor 6| is caused to operate at medium speed. When the contacts are set to a point diametrically opposite tap 15, the maximum of resistance I9 is brought into the circuit of motors 6|, thereby causing the latter to operate at its minimum speed, while at the same time primarily one quarter of the resistance i8 is placed in the circuit of motor which will operate at its medium speed. The reverse takes place when contacts 99 and 8| are diametriof bar 43. Section 29 of the quadrant III is connected by lead 94 with brush 19 of signal producer or interrupter 69. Thus the'audible signal in the earphones will be dot-dash or the letter A." A branch 94' from lead 94 connects with section 29 of quadrant IV, and if indicator 49 would be in the groove of contact bar leg 44, an A signal would also be heard.

Brush 69 of interrupter 61 is connected by leads 95 and 95 to section 21 of quadrant III, and through the continuation oi lead 95 to section 39 of quadrant IV.

The area within the four quadrants'I, II, III and IV, is provided with compass graduations of 360 degrees in a complete circle, which graduations correspond to that provided on the com-.

- pass rose device of the pupil-manipulated. concally opposite tap 84. Motor 9| will then op- I erate at its minimum speed, while motor 6| will rotate at its medium speed. The importance of this arrangement will become more clearly evident under the heading Operatiorifi Audio circuit The other or second conductor 84', connected with the source of energy l3, branches off. at 85 'and leads to motor 65 of the signal emitting instrumentality, while wire 86 passes from motor 66 to branch 19 of conductor 12. Note that conductor 94 is grounded.

Another leg 91 of conductor 94' leads to oscillator 1|, and a wire 98 reverts to branch I9 of conductor 1.2. From signal wheels 69 and 19 passes an input wire 99 into oscillator 1|, and an output wire 99 is connected with earphones 22. From the earphones current is passed through individual, hand-adjustable volume control 29, and from there by lead 9| to central tap 64 of resistance 69. From this tap current flows through a portion of resistance 64 to glide contact 62, mounted at the bottom of bar 59. Glide contact 63 of bar 5|, riding over resistance 65, is connectedby lead 92 with contact 62, whereby current is conveyed from contact 62 to contact 63, through a portion of resistance 65 to its tap 65'. This tap is connected by lead 93 with pin 41 of indicator 49. From the latter audio current is directed through either of the two conductive legs of contact bar' distances from the range station.

A shown in Fig. 2, sections 25 and 28 of quadrants II and III, at the right-hand upper corner oithe device, are in electric contact with leg 95 trol instrument at H. The graduations within the quadrant circle also serve for varying the positions of the legs to represent any particular radio range station. Such adjustment is made by the instructor. For the purpose of better understanding the graduation in Fig. 2 i shown in a circle within resistances l8 and I9.

It is assumed that the top edge of casing l9,

99 and- I99, and point approximately West and v t n I I Operation Fromthe diagram in Fig. 2 it is evident that resistances l8 and I9 control the motor speeds of variable motors 6 and GI. Obviously another set of two resistances may be added for controlling the' speeds of motors 59 and 59' if desired.

Indicator 49, representing an airplane in flight, is the object which is to be directed by the pupil pilot in accordance with the instruction of the teacher. This indicator is placed at the junction of slotted control bars 59 and 5| and engases with its conductive extension 41 contact bar 43. When either or both of control bars 59 and 5| are moved, these movements are imparted to indicator 49, which in turn will move in a direction induced by the movements of the control bars. Thus when bar 59 is caused to move upwards or downwards, while bar 5| is stationary, indicator 49 will move in northward or southward directions. When bar 5| moves from right to left or left to right, while bar-59 is stationary, indicator 49 will move either in westerly or easterly directions. By a combined movement of both bars, indicator 49 will follow a course corresponding to the resultant of the compound movements of bars 59 and 5|. When it is desired to actuate one of the slotted control bars, say bar 59, while bar 5| remains stationary, such movement is produced by increasing or decreasing the speed of slotted shaft 54 in respect to the constant normal speed of threaded shaft 53, while both shafts 53' and 54' of bar 5| are kept turning at normal speed.

Referring to Fig. 4, assume now that shaft 53 revolves at normal speed clockwise while shaft 59 revolves at a lower speed counterclockwise. In that case gear housing 52 with the gears and bar 59 will move toward the observer. When shaft 54 is now turned at a higher speed than shaft 53, the movement of bar 59 will be reversed. When the speeds of both shafts are equal, the entire assembly will be at a standstill. It is of course assumed in this case that the gear ratio is one to one. By changing that gear ratio differ.-

ent movements or guide bars 50 and II will result.

For the purpose of better understanding it is assumed that the normal speed of both shafts is 100 R. P. M., and that the movement 01' threaded gears 55 is one inch per minute at that speed. Assume further that the threaded shaft or spindle is provided with 16 threads per inch. Thus it will be necessary to increase the speed of shaft 54 to 116R. P. M. in order to impart to bar 50 a movement or one inch per minute in the direction away from the observer. when, on the othenhand, the speed of shalt S4 is reduced to 84 R. P. M., bar 50 will move towards the observer at the rate of one inch per minute. Inasmuch as resistance l9 controls the speed of motor 6! within the range from 84 R. P. M. to 116 R. P. M., any rate of movement of bar Ill, ranging from zero to one inch per minute in either direction may be obtained. A

The same arrangement applies to motor 6! controlled by resistance l8. Through the combined control of speeds of motors 5i and GI, bars 50 and 5| may be moved in either direction singly or in conjunction with one another, whereby flight indicator or rider 49 is accordingly positioned in respect to the area within the quadrant rs. It now the instructor requires the pupil pilot to move the plane, represented by indicator 49, in due north direction, the pupil will bring his control instrument, by the use of hand wheel Hi, to a. zero setting which corresponds to north. By so doing bar 5i will remain stationary, whereas bar 50 will move upwards, taking with it indicator 49.

'The northward movement of bar 50 is caused by the fact that when the control instrument is set to zero, contact 80, riding over resistance l9, will rest against tap 15, whereby resistance I9 is completely eliminated and the full current passes to motor 6|, which motor, when thus superence being had to Figures 2, 3, :7, 8and 9.-- Itplied by the full current, will revolve shaft 54 at the maximum speed of 116 R. P. M. At the same time contact 81 is placed over one-quarter of resistance i8, whereby motor 6i will operate at its medium speed, at which shaft 54' will rotate at 100 R. P. M., which rate of rotation is that of shaft 53'. Consequently bar 5i will be at a standstill, and only bar 50 will move northwards. When contacts 80. or 8! are placed opposite tap 15, the indicator will move south; when the contacts are placed opposite tap 84, the indicator will move westward. At settings of glide contacts 80 and 8| to any other position between the taps, varying speeds are imparted to motors 6i and GI, whereby bars 50 and 51 will accordingly change their respective positions. In this manner indicator49 may bebrought to any desired point in respect to the simulated radio station.' Obviously. the arrangement of the glide contacts and resistances may be altered for producing other types or combinationsof movement of the bars; especially such changes will be required when motors 59 and 59' are intended to have variable speeds also.

In order to prevent the movement of bars 50 and 5! beyond their intended travel over their simulated field, suitable spring equipped end stops 538 are provided with the threaded spindles 53 and 53'. The threads of the spindles end a short distance from stops 53S, and the springs of the stops tend to bring gears 55 into operative engagement with the spindle threads when the 32 at right.

Radio signals the airplane, the present arrangement is so conand IV, carry the signal "N." 'Thus when indicator 49 is caused to move between radio legs 91 and "ill, or legs 98 and 88, signal A will be audible to the student pilot. When theindicator travels between legs 98 and M0, or legs "and 98, the N" signal is heard. 7

The audibility of these signals will change with the distance of indicatorfrom the broadcast station, represented by the center 48 or bar 42. This change of audlbility is'caused by the movement of bars 50 and Si in respect to resistances 64 and 65, which latter are in the audio circuit.

- The further away brush contacts 82 and II of the bars are from center taps'64 andti'iof the resistances, the more resistance is placed in the circuit, and the weaker the signals will become. As the bars move nearer to the station, the signals will gain in strength.

When the indicator is brought within any one of the four leg cones 91, 98, and I00, the signal reception will become considerably altered, refhad been stated previously that each two adja: cent sections of each quadrant are bridged by resistances 32, over which ride brush contacts 44' or 45' of contact bar legs 44 and 4!, respectively. As indicator 48 is moved into any or the cone areas, and its movement gradually progresses towards the center or separating point between the quadrant sections, one of the brush contacts will engage the bridging resistance at one of its ends and move towards its middle. The moment a portion of the resistance is brought into the audio circuit, both signals "N" and .A" will be received, the weaker being keyed in to produce an underlying on-course" signal. The composite being the bi-signal or twilight zone."

Assume that the indicator in Fig. 2 moves in clockwise direction as it approaches leg' I00. Signal A is heard alone until arm 45 of bar 42 reaches a position over the bridging resistance As arm contact 45' touches the end of the resistance, signal A" still will "be heard very strongly, but signal N" will be received, although faintly. At that position the indicator will be'in the "A bi-signal zone.

As now the indicator progresses towards the separation of sections 25 and 28, or towards the middle of the bridging resistance, the "A signal will become gradually less audible; whilejthe strength of signal N will incr'easejv When, the indicator is placed in a position at which brush contact 45' nears the middle of the bridgingjresistance, the signals will become nearly equal in strength. At that position the indicator is, in the twilight band bordering the on course" The indicator is in the on course" leg when the brush contact is at the center of resistance '32, at which position the signals are of equal strength and merge to the signal T, a long monotonous dash, I

When the pupil pilot has found the leg, the

problem arises of ascertaining which one of the legs or beams has been encountered, and it is required to identify such beam. There are several methods whereby this is accomplished, such as the 90 degree method, the parallel course method, the outbound course method, which methods are well-known and require no further explanation. These methods may be duplicated in the present device by the pilot student.

Cone of silence In order to simulate the cone of silence,

contact arm 43 is made in two parts connectedby a non-conductive center 46. When the rider or indicator 49 reaches this center the tone slgand vice versa, depending upon the direction of movement of arm 43. The strength of the signals within the segments between the four beams being governed by the movement of bars 50 and 5|, the signals will diminish in strength when r the bars travel from the center points or taps 64 and 55 of resistances 64 and 65 in either direction and will be strongest when the bars are in line with the taps. By this arrangement 'the A and N bi-signal zones, as well as oil'- course areas for A" and N signals are simulated. I

From the above explanation it will be quite evident that all maneuvers of an aircraft in flight, directed by radio range signals emitted ,from a field, may be simulated by the present device. I

Modifications In Fig. 10 a modified form of a contact arm with contacts M and 45'. The operation of the device with the modified contact bar is identical with that explained in connection with Fig, 2, except that the positions of the resistances are changed' I Another modification ofthe flight indicator is shown in Fig. 11, wherein the top or cover II is provided at its undersurface with an exchangeable chart sheet I08, and wherein flight indicator I09 is in the form of a scriber, contacting chart sheet I08 and impressing or recording all movements of indicator I09 upon that sheet, unknown to the pilot student.

In Figs. 1 and 2 the pupil-manipulated control instrument is shown to have means ior manually actuating it. When my apparatus is employed in a classroom a manual control of the type indicated will suillce. 11, however, the entire instructing device is placed, for instance, into a training plane, it is intended that the device be coupled with the gyro compass of such plane, and that the manipulation of'the control instrument takes place through the usual control instruments employed in the plane. For this reason, and because my device-is capable of being adapted for uses other than mentioned,

it is repeated that the illustrations are by no means intended to limit me to the structure shown, and that the device may be altered in order to adapt it for any desired use. Also in other resp cts it is intended to make changes and improvements in the device, especially as applied to the instrumentalities contained in casing I0,

and I therefore reserve for myself the right to make changes and improvements in my invention, all within the broad scope of my invention,

as expressed in the annexed claims.

I claim:

1. In a pilot instructing device or the like, a substantially closed casing having a removable cover intended to simulate a flying field,-a rider movable beneath the cover and intended to simu-' late an aircraft in flight, means associated with the rider for indicating its position in respect to the cover, an electric source of power, a set of four concentrically arranged electrically coopersting, relatively movable quadrant bar units disposed below the operating area of the rider, each unit comprising two arcuated electric conductors joined by a fixed electrical resistance, the conductors of each two adjacent units contacting with and overlapping one another, a rider support and guide centrally pivoted in respect to the quadrant bar units and comprislngltwo centrally insulated conductive rider guides in gliding contact with the quadrant bar units, a pair of rideroperating bars movable at right angles to one another and electrically insulated from the rider,

insulated glide contacts provided with the bars,

electrically actuated means for operating said rider-operating bars and said glide contacts, electrically operated sound producing instrumentalities ior emitting A and N signals, electric sound receiving means for said signals, variable resistances interposed between said sound producing and said sound receiving means, and being engaged by said glide contacts of the rider- 'operating bars, the intensity of the signals being governed by the position of the glide contacts in respect to the variable resistances and by the position of the rider support in respect to the fixed resistances connecting the conductors of the quadrant bar units, a compass rose-representing variable resistance unit for controlling the operating means for said rider-operating bars; said electric power source energizing two circuits, one including the set of quadrant bar units, the rider support, the variable resistances, the sound producing instrumentalities and said sound receiving means, and the other circuit including the electrically actuated means for the rider-operating bars and said ,variable resistance unit.

2. In a pilot instructing device or the like, a

without the casing for thereceptionoi t ese signals, other means within'the casingjftor ,control'n g the intensity 0! the signals accordingfito the position 01' the rider in respect to' the"cov,er. means operative within the casing tor-positioning the rider in respect to the cover,

means without the casing for controlling said rider positioning means and representing a compass rose, "and an electric power-source supplying current to said signal producing and said rider positioning means, said rider positioning means comprising two cooperating rider-engaging memcasing having a removable cover, thelatter representin'g a dying field, a rider-"operative beneath the cover and representing an aircraft in flight andhaving means for defining its 'positio'nin rereset to the cover, "electric signal emitting means and an electrically operated mechanism torposi- "the rider in respect to 'the'cover within the casing. and-signal receivingimeans andcontrol means for said mechanism without the cas tially the entire length or the shalt. individual electric'motors driving the-shalt series, the operation and speed or the motors being governed by said control means, an intermeshed gear assembly operative with each shaftseries and comprising an internally threaded g'ear engaging the threaded shaft and smooth-bore gear having a mg, said control means representing a compass and means "interposed between said signal emitting and signal receiving means for govern-.

ing the intensity of signals, said rider operatingmechanism comprising at least two series of parallel shafts disposed at rightangle to each other, each shaft serie's being composed of a threaded shalt and a smooth shaft, the. latter having a keyway extending longitudinally along substankey and-being in gliding engagement with the V smooth shaft, the gear key being guided in the keyway of that shaft; at least two'rider-operating bars movable at right angles to each other, one of said gear assemblies fixedly associated with each bar and facilitating the movement or one bar relative to the other through the operation of the shaft series.

'4. In a pilot instructing device or the like, as

per'claim 3, said signal intensity governing means comprising variable resistances extending along said shait series and being engaged by a gliding contact associated with each rider=operating bar. a set oi. tour concentrically arranged electrically cooperating quadrant bar-units disposed below the operating area oi the rider and, being ad- Justahle relative" to each other, each unit comprising two arcuated conductors Joined by fixed resistances, the conductors of each two adjacent 'units'engaging. and over-lapping one another, a rider support and guide centrally journaled relative to said quadrant bar units and comprising a two aligned conductive arms insulated from each other at their joum'aled center, the arms being in gliding contact with the quadrant bar the positioning of the rider-operating bars "in.

respect to the variable resistances and the loca 8' tion of the rider support arms in respect to the fixed resistances joining the quadrant bar unit 'conductors determining the strength of the signals audible in the signal receiving means.

, HARLOW B. GROW. 

